ES2861380T3 - Manufacturing procedure of a photovoltaic module that has low resistive losses - Google Patents

Abstract

Method of manufacturing a photovoltaic module that successively comprises the following steps: - providing photovoltaic cells (10) that include collector fingers (12); - cutting (F1) the photovoltaic cells (10) according to a first direction (41) perpendicular to the collector fingers to form a plurality of subcells (40, 70); - aligning (F2) subcells (40, 70) in a second direction (42) perpendicular to the first direction (41), in order to constitute groups (400, 700) of electrically isolated subcells, each group of subcells having one dimension ( L ') in the second direction (42) substantially identical to the dimension (L) of the photovoltaic cells (10) in the second direction; - forming (F3) simultaneously a plurality of chains (410, 710) of subcells connected in series, successively aligning the groups (400, 700) of subcells (40, 70) in the first direction (41) and interconnecting the groups (400 , 700) of aligned sub-cells (40, 70), the sub-cells (40, 70) of each group (400, 700) being simultaneously grasped and belonging to chains (410, 710) of different sub-cells; and - connecting (F4-F5) electrically in series the chains (410, 710) of sub-cells (40, 70).

Description

DESCRIPTION

Manufacturing procedure of a photovoltaic module that has low resistive losses

Technical field

The present invention concerns a method of manufacturing a photovoltaic module, in which the photovoltaic cells are divided into sub-cells and the sub-cells are connected in series in order to reduce the electrical current generated by the module and to increase the voltage between its terminals. .

State of the art

A photovoltaic module comprises a multiplicity of identical photovoltaic cells connected in series and / or in parallel in order to supply at their output the voltage and / or current required to power electrical devices. The most common module format uses 60 square (or “pseudo-square”) cells, 156 mm on a side, divided into six “strings” of ten cells connected in series. Also, the six strings of photovoltaic cells are connected in series. The open circuit voltage across the module's terminals is then equal to 60 times the threshold voltage of a photovoltaic cell. For example, with silicon homojunction photovoltaic cells that have a threshold voltage of the order of 0.65 V, the open circuit voltage across the module terminals reaches approximately 39 V.

Since all the photovoltaic cells of this module are connected in series, the electrical current of the module corresponds practically to the current supplied by each photovoltaic cell (for practical purposes, the photovoltaic cells do not have exactly the same efficiency and the electrical current comes from limited by the least efficient cell of the module). With the latest photovoltaic cell technologies, especially PERT technology (for “Passivated Emitter and Rear Totally diffused” in English), the current of a monofacial cell with a surface area of 156 x 156 mm2 reaches high values, of the order of 9 A for a solar irradiance of 1000 W / m2. These current values increase by approximately 20% when using a bifacial cell, due to diffuse solar radiation captured on the back of the cell.

The photogenerated charge carriers, which contribute to the electrical current of the photovoltaic cell, are collected thanks to a network of electrodes deposited on the front face of the cell. These electrodes, also called collecting fingers, are narrow (<100pm). They are generally formed by screen printing of a silver containing paste. The back face of the cell is either covered with another array of electrodes (in the case of bifacial cells), or with a full metal layer, for example with aluminum (in the case of monofacial cells). The electric current then flows through interconnections from one cell to another in the chain.

Today, two major techniques are distinguished for interconnecting photovoltaic cells in a chain: interconnections in the form of a strip and interconnections in the form of an electrical wire. These two techniques are represented respectively by Figures 1 and 2.

In Figure 1, the interconnections between cells 10 are formed from copper strips 11 coated with a fusible alloy, typically a tin-lead alloy or a tin-silver alloy. These strips 11 of rectangular section are welded onto conductive tracks called "connecting bars" (or busbars) and shaped at the same time as the collector fingers 12 by screen printing. The connecting bars electrically connect the collector fingers 12 and are oriented perpendicular to the collector fingers 12.

A 156mm x 156mm cell generally has three 1.5mm wide strips or four 1.2mm wide strips, these strips having a thickness of the order of 0.2mm. Each strip 11 connects the front face of a cell 10 with the back face of the next cell in the chain (not shown in Figure 1). The series placing of the photovoltaic cells 10 by means of the strips 11 is carried out in a completely automated way, in a device called "stringer".

Several equipment suppliers now propose to replace the copper strips with electrical wires with a smaller section. For example, the “Multi-Busbar” technology developed by the firm “Schmid” and described in the article [“Multibusbar solar cells and modules: high efficiencies and low silver consumption”, S. Braun et al., Energy Procedia, vol. 38, pp. 334-339, 2013] multiplies the number of connection bars deposited on the cell, going from three to fifteen connection bars, and welds a 200 pm diameter wire to each connection bar. This technology is outlined in Figure 2. The wires 20 are made of copper and covered with a thin layer of an alloy based on tin-lead or tin-silver whose melting point is above 170 ° C. The connecting bars have a discontinuous shape. They are made up of metallization tabs 21, approximately 500 pm x 700 pm, aligned on the collector fingers 12. The metallization tabs 21 and collector fingers 12 are generally made by screen printing of a silver paste. The welding of the wires 20 on the tabs 21 takes place immediately after the wires have been placed on the tabs, in the same equipment, heating these elements to a temperature of the order of 200 ° C. In this way, the alloy that covers the copper wires is melted.

The “SmartWire” technology, developed by the firm “Meyer Burger” and described in the article [“Smart Wire Connection Technology”, T. Sóderstróm et al., Proceedings of the 28th European Photovoltaics Solar Energy Conference, pp. 495 499, 2013], consists of depositing a wick of 18 to 36 threads of 200 gm or 300 gm in diameter directly on the collector fingers. In other words, photovoltaic cells are devoid of connecting bars. The threads are supported by a support film of polyethylene terephthalate (PET), which is glued on each face of the cells. The wires have a copper core and an outer coating made of an indium-based alloy. This alloy has a melting temperature lower than 150 ° C, which allows the electrical connection between the wires and the collector fingers, not so much in the interconnection stage of the cells (by localized heating around 200 ° C) , but rather in the lamination stage of the photovoltaic modules (which is carried out at a lower temperature, generally around 150-160 ° C).

The interconnections in the form of an electric wire make it possible to reduce the length of the collector fingers with respect to the configuration of three connecting bars (Fig. 1), since the number of wires is greater than the number of strips. This increase in the number of interconnections does not necessarily have an impact on the shading of the photovoltaic cell due to the smaller size of the wires. On the contrary, it allows to considerably reduce the amount of silver used to print the collector fingers. In effect, since the collector fingers are shorter, it is possible either to reduce the width of the fingers, or to use a paste that is less rich in silver (and therefore less conductive) for an equivalent series resistance. Additionally, thanks to their circular section, the electric wires have an effective shading on the photovoltaic cell equal to only 70% of their diameter, against 100% of the width of the strips. Thus, for a set of interconnections having the same cross section, the percentage of shading on photovoltaic cells interconnected by wires is lower than that on photovoltaic cells interconnected by strips.

The collector fingers are the cause of resistive losses that distort the filling factor (FF) of the photovoltaic cell and, therefore, its performance. Remember that the fill factor FF represents the "deviation" of the real I-V characteristic of the cell from an ideal rectangular characteristic. Its expression is the following:

Popt

FF

Ice x Vco

where P ^opt is the power supplied by the cell at the optimum operating point of the true IV characteristic, I ^cc is the short-circuit current and V ^co is the open-circuit voltage. Cell performance n is related to fill factor FF by the following relationship:

I see ■ 1cc ■ FF

where P, is the power of the incident solar radiation.

To these resistive losses in the cell domain, we must add the resistive losses in the module domain, that is, in the interconnections. The resistive losses in the interconnections are proportional to the square of the electrical current I generated by the module and to the series resistance RS of the interconnections, which in particular depends on the copper section used.

Therefore, a solution to reduce these resistive losses would consist in increasing the section of the copper strips or wires to decrease their series resistance R ^s . However, this solution is rarely implemented due to two major drawbacks. Increasing the copper section (especially through its thickness) would lead to an increase in mechanical stresses in the interconnections (due to the difference in the coefficients of thermal expansion between copper and silicon), which would be detrimental to reliability of the modules. Increasing the copper section through its width would have a negative impact on the percentage of shading of the photovoltaic cells.

Figure 3 illustrates a more efficient way to decrease resistive losses in the interconnections by connecting half cells 30 in series, that is, photovoltaic cell halves, rather than whole cells. Indeed, by dividing by two the surface of the elementary cells that make up the chains of the module, the electrical current of the module is also divided by two. The resistive losses in the interconnections are then reduced by a factor of four. The number of elementary cells in the module is generally multiplied by two, in order to double the voltage across the module's terminals and keep the same module size.

The half cells 30 are produced by cutting entire photovoltaic cells 10 parallel to the collecting fingers 12 (cf. Fig. 1), for example, by means of a laser. Next, the half cells 30 are connected in series in the same way as whole cells. Today, stringer-type equipment adapted to the format of the half-cells is marketed to form chains of half-cells, such as the one represented in figure 3. These equipment work with copper strips 11 according to the usual configurations of 3 or 4 connection bars. .

In this way, instead of a module comprising 60 standard-size photovoltaic cells (for example, 156mm x 156mm), a module can be manufactured comprising 120 half-cells (156mm x 78mm) all connected in series. . Modules based on half cells generally have a better fill factor than modules based on whole cells and consequently a higher electrical power P ^opt (at constant cell surface).

As a counterpart to this better efficiency, the speed of the photovoltaic module manufacturing lines is reduced by half, as the stringer must handle twice as many elementary cells.

It is seen, then, that the current equipment constitutes a brake for obtaining photovoltaic modules that have even lower current values and, therefore, very limited resistive losses. Indeed, the production rate, if divided by two when using half-cells, is divided by four by connecting in series quarters of cells cut parallel to the collector fingers. However, developing new equipment is not only slow and risky for equipment suppliers, but it would also force manufacturers of photovoltaic modules to replace their machine parks.

On the other hand, documents WO 2013/020111, US 2013/139871 and DE 102008043833 describe processes that make it possible to manufacture flexible and high-voltage photovoltaic modules. Also, these procedures envisage using sub-cells cut from full-size photovoltaic cells. The cut is carried out by means of a laser, after having glued glass or Teflon sheets with the dimensions of the sub-cells to the front face of the photovoltaic cell. The touchdown on the rear face is formed for each subcell after trimming. The cells are then interconnected in series and laminated between flexible anterior and posterior plates. Photovoltaic cell interconnection systems in a module are described in DE 102012220221, US 2007294883 and US 2003127124.

Summary of the invention

There is a need, both for module manufacturers and for their equipment suppliers, to be able to manufacture photovoltaic modules with lower electrical current, without having to completely change the current equipment and without further reducing the production rate of these modules.

According to a first aspect of the invention, the aim is to satisfy this need by providing a photovoltaic module manufacturing process according to claim 1 that successively comprises the following steps:

- foresee photovoltaic cells that include collector fingers;

- cutting the photovoltaic cells according to a first direction perpendicular to the collector fingers to form a plurality of subcells;

aligning subcells in a second direction perpendicular to the first direction, in order to form groups of electrically isolated subcells, each group of subcells having a dimension in the second direction substantially identical to the dimension of the photovoltaic cells in the second direction;

- aligning the groups of sub-cells in the first direction, manipulating the groups of sub-cells one by one, and interconnecting the groups of sub-cells in order to form a plurality of chains of sub-cells connected in series, the sub-cells of each group belonging to different chains of sub-cells; and

- electrically connect the chains of sub-cells in series.

In order to more economically manufacture photovoltaic modules with low electrical current, a process is proposed in which pieces of photovoltaic cells called "sub-cells" are arranged close to each other and are manipulated in groups, in order to simultaneously form several chains of sub-cells. . On the other hand, in the manufacturing processes of the prior art, the chains of sub-cells are formed one at a time, since the sub-cells (cut in the same direction, parallel to the collector fingers) are handled individually.

Thanks to the fact that the groups of sub-cells retain one of the standard dimensions of photovoltaic cells (for example, the dimension “156 mm”), the current stringers can be used to connect the sub-cells of each chain in series. These kits only require a few small modifications to manipulate groups of sub cells, rather than half cells or whole cells. In this way, equipment suppliers will be able, at a lower cost, to adapt existing machines and respond effectively to the needs of low-current photovoltaic modules.

For example, by cutting each photovoltaic cell into 2, 3 or 4 sub-cells according to the first direction only, that is to say, perpendicular to the collecting fingers of the cell, the method according to the invention makes it possible to form, respectively, 2, 3 or 4 chains of sub-cells in as long as a whole cell chain, using a whole cell stringer. The production chain for photovoltaic modules is then long. In the case of "half-cell" modules especially, this is doubled with respect to the manufacturing process of the prior art.

In a preferred mode of implementation of the method according to the invention, the photovoltaic cells are trimmed once in the second direction, that is, parallel to the collector fingers, and at least once in the first direction, that is, perpendicular to the collecting fingers. In this way, when the cells are cut first in the second direction, two half-cells (of equal surface area) are obtained, within which the sub-cells are then cut.

This way of putting it into practice makes it possible to form several chains made up of sub-cells, of a smaller format than that of half-cells, in as much time as a chain of half-cells thanks to a half-cell stringer. In this way, photovoltaic modules can be manufactured with lower current values than that of a half-cell module, without further reducing the production rate.

The method according to the invention can also have one or more of the following characteristics, considered individually or according to all technically possible combinations:

- the groups of subcells are interconnected two by two by means of electrical strips so that each face of the subcells is in contact with at least one strip;

- the electrical strips have a width of less than or equal to 1 mm and a thickness of less than or equal to 180 gm;

the groups of subcells are interconnected two by two by means of electrical wires so that each face of the subcells is in contact with a plurality of electrical wires;

- the electric wires are integral with a support made of polymer material and contact the collector fingers of the sub-cells;

- the groups of sub-cells are interconnected by pressing a support sheet on both sides of each group of sub-cells, the electrical wires being distributed on the surface of each support sheet in contact with the group of sub-cells, and in which the support sheets they are subsequently trimmed to separate the different chains of sub-cells;

- The groups of sub-cells are interconnected by pressing several differentiated pieces of the support on both sides of each group of sub-cells, electrical wires being distributed on the surface of each piece of the support in contact with the group of sub-cells, and in which each piece of the support belongs to a single chain of sub-cells;

- the electric wires have a diameter less than or equal to 200 gm;

- the sub-cells belonging to the chains of sub-cells connected in series are of the same type and are oriented in the same direction;

- the sub-cells belonging to a first chain and the sub-cells belonging to a second chain adjacent to the first chain are of opposite types or are oriented in opposite directions;

- the sub-cells belonging to the chains of sub-cells connected in series have the same surface area; - the subcells of a group originate from the same photovoltaic cell; and

- each group of sub-cells comprises 2, 3, 4 or 5 sub-cells.

A second aspect of the invention concerns a system according to claim 11 that makes it possible to interconnect photovoltaic cell portions, the photovoltaic cell portions comprising collector fingers oriented perpendicular to a first direction. This set includes:

- a charging station configured to distribute groups of several electrically isolated cell portions aligned in a second direction perpendicular to the first direction, each group of cell portions having a dimension in the second direction substantially identical to the dimension of the photovoltaic cell in the second direction;

- a station for assembling the groups of cell portions into a plurality of chains of cell portions;

- a first transfer unit configured to capture each group of cell portions and move said group of cell portions from the loading station to the assembly station.

The interconnection system according to the invention may also have one or more of the following characteristics, considered individually or according to all technically possible combinations:

- the first transfer unit comprises suction nozzles configured to simultaneously suck all the cell portions of said group;

- the interconnection system comprises a station for cutting photovoltaic cells into cell portions, located upstream of the charging station;

- the interconnection system comprises a module for distributing electrical wires integral with a support, and in which the assembly station is configured to mechanically link the support of the electrical wires with the groups of cell portions;

- the interconnection system comprises a cutting device configured to cut the support of the electric wires after assembling the groups of cell portions, in order to separate the chains of cell portions;

- the interconnection system comprises a second transfer unit configured to individually grasp each of the chains of cell portions coming from the assembly station and to rotate said grasped chain 180 °; and

- the interconnection system comprises a second transfer unit configured to collectively grasp several chains of cell portions coming from the assembly station, to release a first part of said grasped chains and to rotate 180 ° a remaining second part of said grasped chains .

Brief description of the figures

Other characteristics and advantages of the invention will be clearly deduced from the description that follows, by way of indication and without any limitation, with reference to the accompanying figures, of which:

Figures 1 and 2 schematically represent two photovoltaic cell interconnection techniques according to the prior art;

Figure 3 represents a chain of elementary cells of a photovoltaic module according to the prior art, where the elementary cells are constituted from half cells;

Figures 4A to 4E represent manufacturing steps of a photovoltaic module comprising a multiplicity of subcells, according to a preferred way of putting the method according to the invention into practice;

Figure 5C represents a variant of implementation of the sub-cell interconnection stage represented in Figure 4C;

Figure 6 represents a photovoltaic module obtained at the end of a variant of the manufacturing process according to the invention, the subcells of this module not being oriented in the same way; and

Figure 7 schematically represents a second mode of putting into practice the manufacturing method according to the invention.

For greater clarity, throughout the set of figures, identical or similar elements are indicated by identical reference signs.

Detailed description of at least one embodiment

In the description that follows, a succession of photovoltaic subcells mechanically joined and intended to be electrically connected in series is called a "chain of sub-cells". Subcells designate chunks of cell trimmed from full-size photovoltaic cells.

With reference to FIGS. 4A to 4E, a first preferred mode of putting into practice the method of manufacturing the photovoltaic module according to the invention will now be described. Face F of the photovoltaic cells and sub-cells represented in these figures is the front face, that is, the face intended to be exposed to incident solar radiation. In the particular case of bifacial cells, as both faces can capture solar radiation, the front face is the one that allows the maximum electrical current to be obtained when it is directed towards the incident radiation.

Figure 4A illustrates a first stage F1 of the manufacturing process in which full-size photovoltaic cells 10 are cut to form sub-cells 40. The photovoltaic cells 10 are provided, at least on the front face F, with a network of collector fingers 12. The collecting fingers 12, in a conventional way, are distributed over the entire surface of the cells 10. They are all oriented perpendicular to a first direction 41.

Previously, photovoltaic cells 10 have been manufactured from semiconductor substrates, for example silicon. They preferably have a square shape or, as shown in Figure 4A, a pseudo-square shape. In the pseudo-square format, the four corners of cells 10 are truncated or rounded. The photovoltaic cells 10 are of standard dimensions, for example 156mm x 156mm.

In this preferred mode of implementation, the photovoltaic cells 10 are first cut into two parts 30 of equal surface area, called "half cells", in a second direction 42 parallel to the collector fingers 12. In this way, two halves of cells are obtained having a length L equal to 156 mm and a width l equal to 78 mm. The width of the half cells 30 and of the sub cells 40 is measured in the first direction 41 and their length is measured in the second direction 42.

Each half-cell 30 is then cut out according to the first direction 41 into several sub-cells 40. This cut-out is advantageously carried out in such a way that all sub-cells 40 have the same surface area. In this way, the sub-cells will produce substantially the same electrical current and a chain formed by these sub-cells will not show a limitation of its current by a smaller sub-cell. When the initial photovoltaic cell 10 is of a pseudo-square format, the sub-cells 40 corresponding to the sides of the half-cell 30 have a length L ^sc slightly greater than that of the sub-cells taken inside the half-cell, in order to compensate for their truncated corner. When the initial photovoltaic cell 10 is square format, the subcells 40 all have the same length L ^sc .

By way of example, each sub-cell 40 represents a quarter of the surface of an entire photovoltaic cell 10 when the half-cells 30 have been cut in two (in the lower right part of Figure 4A), a sixth of the surface of a cell 10 when the half-cells 30 have been cut into three (in the right center part of Figure 4A) and one eighth of the surface of a cell 10 when the half cells 30 have been cut into four (in the upper right part of Figure 4A) .

The trimming of the subcells 40 can be carried out in different ways, for example by sawing, determining a groove with a laser with subsequent cleavage of the cell, or by means of a laser technique called TLS (for “Thermal Laser Separation” in English), which it is based on a thermal separation initiated by a laser. The TLS technique is particularly advantageous, since the laser used does not cause the silicon to melt. Additionally, trimming a photovoltaic cell 10 can be performed in a single operation thanks to this technique. Thus, it is not mandatory to first cut the photovoltaic cell 10 into half cells 30 to obtain the sub cells 40.

In the case of using a laser, the beam advantageously engraves the opposite side to the emitter of the photovoltaic cell 10 to be cut, in order to avoid the risks of a short circuit. The cleavage can be obtained in alignment with the areas embrittled by the laser, for example by pressing these areas with an elastomeric material, when the photovoltaic cell is resting on a non-flat support. Alternatively, a device with moving parts can be used which, holding each future sub-cell by depression, allows bending stresses to be exerted on the breaking axes of the cell by means of a controlled movement of the moving parts. Due to the clamping of each of the sub-cells, the arrangement of the sub-cells from the same photovoltaic cell can be controlled, which facilitates the next stage of the procedure.

The trimming is advantageously carried out in a completely automated way by means of a robot that is part of the production line of the photovoltaic modules, either upstream of the stringer, that is, the equipment destined to form the chains of sub-cells, either in the same stringer sinus. In other words, the stringer may include a station for cutting the photovoltaic cells into sub-cells according to step F1.

The subcells 40 obtained at the end of stage F1 are advantageously classified, for example by photoluminescence (to detect cracked subcells) and / or according to their IV characteristics, in order to discard the subcells likely to limit the efficiency of the module. photovoltaic. The subcells 40 that have a truncated angle can also be separated from those that are devoid, in order to make two types of module.

In step F2 represented by FIG. 4B, the subcells 40 are aligned in the second direction 42 to form groups 400 of subcells. The subcells 40 of each group 400 are spaced a short distance from each other, for example 1mm, in order to be electrically isolated. The number of subcells within each group 400 varies as a function of their length L ^sc . Indeed, the subcells 40 are arranged in such a way that the groups 400 of subcells have a length L 'substantially identical to the length L of the half cells 30 (in the present case, L' = 158 mm, instead of L = 156 mm). The width 1 'of the sub-cell groups 400 is equal to the width 1 of the half-cells (78 mm), in turn equal to the width of the sub-cells 40 (cf. FIG. 4A).

In other words, in step F2, a half-cell 30 is recomposed, juxtaposing as many sub-cells 40 as have been cut from the half-cell 30. In the example represented in figure 4B, the half-cells 30 have been cut into three, so that each group 400 contains three subcells 40.

The distribution of the subcells 40 into groups 400 can be carried out by a robot equipped with a gripper arm associated with a vibrating groove device and, possibly, with an optical detection device that allows it to visualize the subcells before grasping them. The gripper arm grabs the sub-cells coming from the trimming station and places them in the grooves of the vibrating device located in an inclined position. The vibrations coupled to the slope make the subcells slide along the grooves whose width decreases to a dimension just greater than those of the subcells, these grooves being separated by the desired spacing for the subcells. Preferably, this robot is part of the stringer and, more particularly, of the charging station in charge of distributing the groups of subcells. On the contrary, when it comes to specific equipment, additional manipulation of the sub-cell groups is required in order to make them reach the stringer loading station. There is a risk that the arrangement of the subcells in the group will be modified, and the risk of breakage of the subcells is higher.

In order to limit as much as possible the movements of sub-cells between the trimming station and the training station of the groups 400, and thus the risks of breakage of these sub-cells, the sub-cells of a group 400 are taken from the same half-cell 30. In other words, just after being clipped, the subcells are grouped together.

When the cutting system makes it possible to directly position the subcells 40 in the form of groups 400, in the case of the previously described moving parts device or the TLS equipment, for example, the cutting system is advantageously connected to the stringer charging station to in order to preserve the position of the sub-cells.

Next, in step F3 of FIG. 4C, the stringer, with the aid of a robot or transfer unit, manipulates the groups of sub-cells, as it would do with half-cells, to simultaneously form several chains 410 of sub-cells. Thanks to the fact that the groups of sub-cells have practically the same dimensions as the half-cells, the manipulation of the groups instead of the half-cells does not pose any difficulty. It does not require more than a few small modifications to the robot for moving a stringer adapted to the format of the half cells. In particular, the configuration of the suction nozzles of the half-cells is modified to simultaneously grip the sub-cells of each group. One or more suction nozzles per sub-cell can be provided. Given the small caliber of the sub-cells, the suction nozzles are arranged so that each nozzle sucks a sub-cell 40 around its center. The stringer's optical sensing device can also be adapted to properly position the sub-cell groups 400.

Thus, the groups 400 of sub-cells are moved by the robot from the loading station to an assembly station, to be interconnected there. The chains 410 of sub-cells are constituted by connecting two by two sub-cells 40 from different groups 400. The connections are made in the first address 41. Thus, the subcells 40 of each group belong to different chains 410.

This connection mode is described in detail with reference to Figure 4C which, for clarity, only shows two consecutive groups of sub-cells. These groups carry the references 400A and 400B. Thus, the sub-cell chains 410 will be limited in this example to two sub-cells.

First, interconnects 420A are arranged on the first sub-cell group 400A. The interconnections 420A extend in the first direction 41 and have a length equal to approximately twice the width of the subcells 40. Thus, only a part of the interconnections 420A is in contact with the front face of the subcells 40 belonging to the first group 400A. Next, the second group 400B of subcells is arranged in extension of the first group 400A on the unoccupied part of the interconnections 420A. They are then in contact with the rear face of the subcells 40 belonging to the second group 400B.

On the front face of the group 400B there are arranged, in this example, interconnections 420B shorter than interconnections 420A, for example reduced by half. The placement of the interconnections 420B corresponds to the operation to terminate a chain of sub-cells (string). Likewise, the rear face of group 400A had been brought into contact at the beginning of the sequence (in the manipulation of group 400A by the stringer) with interconnections 420C of half length, which corresponds to the operation to initiate a chain of sub-cells. These interconnections 420B and 420C constitute, in the present case, the ends of the sub-cell chains 410.

The chains 410 often comprise more than two half-cells, in order to raise the voltage at the terminals of the photovoltaic module sufficiently. The operations for placing the groups of sub-cells and the interconnections are then reproduced several times depending on the number of sub-cells to be connected in series. The interconnections 420B deposited on the group of cells 400B are then identical to the interconnections 420A, and then a third group of sub-cells (not shown) is arranged on the free part of the interconnections 420B, etc.

In other words, in the course of step F3, the groups of sub-cells are progressively aligned in the first direction 41, manipulating them one by one. Between two successive manipulations, interconnections are arranged on the last group of sub-cells in the chain. These interconnections extend in the first direction 41 and are distributed homogeneously on the surface of the groups, which makes it possible to simultaneously form several chains of electrically independent sub-cells 410.

Interconnections may be of a different nature depending on the interconnection technique used.

A first technique consists in using electrically conductive strips of rectangular section, for example made of copper. Today, there is a perfect mastery of this technique for whole and semi-cell photovoltaic cells, and uses equipment that is widespread and affordable. The strips are distributed above and below the groups of sub-cells, so that each face of the sub-cells is in contact with at least one strip. The number of electrical strips used to join two consecutive groups of subcells is advantageously 3 or 4.

For example, with a 4-strip stringer, one could obtain either two 410 chains made up of quarter cells (78 mm x 78 mm) connected (two by two) by two strips, or four 410 chains made of of eighths of cells (39 mm x 78 mm) connected by a single strip. With a 3-strip stringer, three sub-cell strings 410 (78mm x 52mm) can be obtained simultaneously, each string containing no more than a single stripe in the second direction 42.

Alternatively, electrically conductive wire interconnection techniques may be employed. The groups of sub-cells are compatible, in particular, with the “Multi-Busbar” technology developed by the “Schmid” firm and the “SmartWire” technology developed by the “Meyer Burger” firm. The conductive wires of circular section constitute more advantageous interconnections than the strips, since they reduce the amount of silver necessary to print the collector fingers (due to their greater number) and cause less shading, to the identical conductor section. Therefore, thanks to this type of interconnections, less expensive and more efficient modules can be obtained.

Like the strips, the electrical wires are deposited, in the “Multi-Busbar” technology, on discontinuous connection bars formed on the front face of the sub-cells 40 and eventually on the back face (in the case of bifacial photovoltaic cells) . Within each chain 410, the subcells 40 are connected two by two by several electrical wires extending in the first direction 41.

With this technology, the electrical wires are soldered on the localized buses of the sub-cells when making the chains (localized heating around 200 ° C to fuse the alloy that covers the wires). The threads, then, become integral with the subcells. Since the threads have been welded, the presence of several threads in the second direction 42 prevents the chains 410 from twisting, rotating around the first direction 41. In contrast, the chains 410 that do not include more than a single strip in the second direction 42 runs the risk of turning on itself when manipulated to be connected in series (steps of Figures 4D and 4E).

In the preferred mode of implementation represented in figure 4C, the interconnections 420A-420C are electrical wires integral with a support, like a wick, and make direct contact with the collector fingers, in accordance with the "SwartWire" technology. ”. The subcells 40, in this case, can be devoid of connection bars, which represents an additional saving in the cost of the photovoltaic module (and, therefore, an advantage over the "Multi-Busbar" technology). The support for the electric wires is preferably a flexible film made of polymeric material, for example polyethylene terephthalate (PET).

As shown in figure 4C, the support of the electric wires 420A that joins the two adjacent groups 400A-400B is preferably distributed in the form of two successive sheets 430A having dimensions similar to those of the half cells. The first support sheet 430A is pressed against the front face of the group 400A and the second support sheet (not visible in Figure 4C) is pressed against the rear face of the group 400B. The wires 420A extend on the surface of the first sheet 430A arranged facing the front face of the group 400A and then on the surface of the second sheet arranged facing the rear face of the group 400B. Thus, the support sheets are arranged on the side of the wires that allows electrical contact of the wires with the fingers of the sub-cells. Between the two groups of subcells 400A-400B, the electrical wires 420 are released from their support, which allows them to pass from the front face of the group 400A to the rear face of the group 400B. The space between the groups of sub-cells 400A-400B is, for example, 2.5 mm, which is the usual space between cells for conventional strands with strip interconnections. With threads, this space can advantageously be reduced.

The electrical wires 420B and 420C determining the ends of the chains 410 are only held by a single support sheet 430B, respectively pressed on the front face of the group 400B and on the rear face of the group 400A.

The backing sheets are preferably glued to each side of the sub-cell groups by slightly heating the polymer material (eg, around 100 ° C). However, despite this operation, the electrical contact between the wires 420A-420C and the collector fingers is not yet established. The electrical contact is preferably operated in a later stage of laminating the photovoltaic modules, thanks to the fact that the electrical wires are covered with a layer of an alloy that has a melting temperature slightly lower than 150 ° C, for example an alloy based on Indian.

Apart from the fact that it allows the cost of manufacturing the cells to be considerably reduced, the “SmartWire” interconnection technique is also the most advantageous from the point of view of the reliability of the photovoltaic modules. The fact is that, in the “Multi-Busbar” technology, the electrical contact between the electrical wires and the sub-cells is made by the stringer, before the sub-cell chains are put in series. Consequently, considerable mechanical stresses are exerted on these electrical contacts when handling the sub-cell chains. Some of the contacts could be broken, for which reason discontinuous connecting bars are needed on the cell. On the contrary, in “SmartWire” technology, the presence of the polymer support improves the mechanical behavior of the sub-cell chains. Indeed, thanks to the gluing of the threads on the supports and of the supports on the subcells, the threads can no longer move. So there is no risk of breaking mechanical connections "threads - collector fingers" when handling the sub-cell chains. This is of greater importance since the electrical connections "wires - collector fingers" are not yet formed at this stage if the chain assembly operation has actually been carried out below the melting point of the alloy covering the wires.

To implement the "SmartWire" interconnection technology, the stringer includes a module for distributing the electric wires, for example in the form of a drum around which the electric wires and their support are wound. This module feeds the assembly station with interconnections as the groups of sub-cells arrive at this station. The assembly station is configured to mechanically link the support of the electrical wires with the groups of sub-cells. It includes, in particular, a heating pressing device to heat the support of the threads and stick it to the subcells.

After the groups of sub-cells have been mechanically related in chains or "garlands", the different chains 410 of sub-cells are decoupled from one another, cutting the support sheets 430A-430B in correspondence with the space that separates the sub-cells of a group. The chains 410 can then be individually manipulated. This cutting of the support can be carried out by means of blades, preferably in the form of a rotating disk, belonging to the stringer. The stringer can also be equipped with a laser to trim the support of the threads.

Whatever the wire interconnection technique used in step F3, the wires 420A are advantageously separated in the second direction 42 by a distance of less than 20 mm, preferably between 4 mm and 12 mm. In effect, reducing the distance between wires makes it possible to correct the resistance voltages of the collector fingers. Therefore, a distance between 4 mm and 12 mm will be used advantageously, the smaller distances being associated with the finer threads to limit shading. Thus, 39 mm long ^subcells (L sc = 39 mm) comprise between four wires of 150 gm in diameter and nine wires of 100 gm in diameter.

In the preferred mode of implementation of Figures 4A to 4E, the subcells 40 of the chains 410 are all oriented in the same way and are all of the same type, for example taken from doped standard emitter silicon photovoltaic cells of type n. In a standard emitter photovoltaic cell, the emitter (ie, the thin layer doped with a type of doping opposite to that of the substrate) is located on the front face of the cell. In contrast, in an inverted emitter cell, the emitter is located on the rear face of the cell. Thus, the type of a cell / sub-cell can refer to the location of the emitter in the cell / sub-cell. Likewise, two types of cells / sub-cells will be distinguished depending on the type of doping of the substrate (n or p). Indeed, a standard emitter cell determined from a n-type substrate can be considered of the opposite type to another standard emitter cell determined from a p-type substrate. Identical orientation means that all subcells 40 have their front face F oriented towards the same side, for example upwards (ie towards the sun).

Under these conditions, it is seen in FIG. 4C that the determining interconnections 420B at the ends of two adjacent chains 410 are of the same polarity. Indeed, all of them are connected to the front face of the subcells belonging to group 400A. The same occurs with the interconnections 420C pressed against the rear face of the subcells belonging to group 400B. Therefore, it seems rational to rotate one of the two sub-cell chains 180 ° before connecting them in series.

Thus, in step F4 of FIG. 4D, a 180 ° rotation of a chain 410 of sub-cells 40 is performed every two chains, without however changing their orientation. In the example of a photovoltaic module shown in Figure 4C, which only has three strings 410, the middle string is rotated 180 °. The ends 420C of the central chain 410 are then on the opposite side, with interconnections 420B of reverse polarity on both sides.

This rotating operation can be carried out by a second robot or transfer unit that takes hold of the sub-cell chains one by one at the exit of the assembly station, in order to place them side by side on a protection plate of glass constituting the front face of the photovoltaic module. In a conventional way, the protection plate formed from the front face glass of the module is covered with a sheet of encapsulating material, before the chains of sub-cells are placed thereon.

Finally, in step F5 of Figure 4E, the different chains 410 of sub-cells are connected in series, locating, for example, at each end of the chains, a conductive strip 440A that extends in the second direction 42 over the interconnections 420B -420C from two adjacent 410 strands. In addition, conductive strips 440B and 440C can be attached respectively to the interconnections 420B of the last string 410 of the series (on the right in Figure 4E) and to the interconnections 420C of the first string 410 of the series (on the left in Figure 4E). The conductors 440B and 440C advantageously constitute the terminals of the photovoltaic module.

Alternatively, the second transfer robot can be configured to simultaneously grasp several chains 410 of sub-cells, eventually pass them under a chain length adaptation device, place some of them on the glass protection plate, rotate the chain chains 180 °. remaining sub-cells, that is, those that the transfer robot has not released and then place the remaining sub-cell chains next to the chains already positioned on the protection plate. For example, in the case of four chains of 410 sub-cells formed simultaneously and set in parallel, the transfer robot grabs the four chains, places the first and third on the protection plate, rotates the second and fourth 180 ° and the it then poses next to the first and third strings, respecting the initial order of the sub-cell strings.

This second robot comprises at least one group of suction nozzles configured to individually grip each of the sub-cell chains, instead of a chain of half cells or a chain of whole cells. In the case of a collective manipulation of the chains, the robot advantageously comprises several groups of suction nozzles. The suction nozzles of each group are controlled simultaneously and arranged in order to suck and hold each sub-cell of the grasped chain. On the contrary, the different groups can be controlled independently of each other in order to grasp and release only a part of the sub-cell chains.

The second transfer robot can be a module coupled to the stringer assembly station and, therefore, form part of the same system, or it can be a separate team, located between the stringer and the layup station on the production line. of photovoltaic modules. The layup station designates the location where the sub-cell strings 410 are moved and where the photovoltaic module is assembled. After having been arranged on the front protection plate of the module, the chains of sub-cells 410 are connected in series (step F5) and, then, covered with a second sheet of encapsulating material and with a second protection plate constituting the face. rear of the module.

Figure 5C represents a variant of implementation of the sub-cell interconnection stage F3 (so-called "stringing" stage), within the scope of "SmartWire" technology.

Instead of trimming the support sheets after having been pressed against the faces of the sub-cell groups, the support sheets have been previously trimmed, that is, before step F3, in the first direction 41, into several pieces 430 '. The pieces 430 'have as a whole the dimensions of a subcell 40. They are joined two by two by interconnections 420A: a piece from the first sheet with a piece from the second sheet. In this way, the stringer is no longer fed with pairs of sheets with a "semi-cell" format, but with a plurality of bands or garlands that each comprise two support pieces 430 'and a part of the interconnections 420A.

In step F3, the pieces 430 'are then pressed against the faces of the sub-cells, preferably in the same sequence as the support sheets 430A (Fig. 4C). For example, to connect a sub-cell 40A belonging to group 400A to a sub-cell 40B belonging to group 400B, a support piece 430 'is pressed against the front face of sub-cell 40A and the other piece (not visible in FIG. 5C) is it presses against the rear face of the subcell 40B (when the group 400B is resting on the interconnections 420A).

This variant of implementation of step F3 makes it possible to directly obtain chains of sub-cells independent of each other, but increases the complexity of the equipment for preparing the yarn locks. The steps F4 and F5 (called "layup") can then be carried out, which allow the series connection of the chains of sub-cells 410, in the same way as previously described, in relation to FIGS. 4D and 4E.

One way to avoid the rotation of the chains of sub-cells in stage F4 of figure 4C and the operation of trimming the support sheets (before or after stage F3) is to use sub-cells of the opposite type or orientation between two chains of adjacent sub-cells 410. Indeed, in these two cases, it is no longer useful to separate the chains of sub-cells 410 formed simultaneously in step F3, since the polarity of the interconnections 420B (or of the interconnections 420C) alternates as it passes from one chain to another. Therefore, these can be moved together towards the layup station, where they are interconnected by the conductive strips 440A.

Figure 6 schematically represents one of these variants of putting the manufacturing process into practice. The subcells 40 of the chains 410 are all of the same type, but their orientation differs. In the stage F2 of constitution of the groups 400, the sub-cells are arranged so that one sub-cell of every two groups 400 is oriented in the opposite direction. In the example of groups of three sub-cells (Fig. 6E), the sub-cell in the center of the groups 400 can be arranged with the rear face B directed upwards, while the two sub-cells at the edges have their front face F oriented towards above.

This first variant of the manufacturing procedure, valid only in the case of bifacial cells, shows an efficiency (in terms of electrical power of the photovoltaic module) that is lower than that of the previous case, in which all the subcells are of the same type and the same orientation. Indeed, it is rare to extract exactly the same electrical current from a bifacial cell regardless of the orientation of this cell. The current is lower when the rear face is exposed to incident solar radiation. This difference in current can be avoided by modifying the dimensions of the subcells, depending on whether they are used on the front face or on the back face, but the resulting current will be less.

The decrease in the current of the cell chains, caused by cells whose rear face B is directed upwards, can be limited by using only photovoltaic cells that have a high percentage of bifaciality, greater than 95%. The bifaciality percentage designates the ratio between the electric current generated by the cell when its front face is exposed to incident solar radiation and the current generated by this same cell when the rear face is exposed to the same radiation.

As noted above, the same benefits can be obtained by alternating sub-cell types between a 410 chain and another, but orienting them in the same way. For example, the subcells of a string 410 may be standard emitter and the subcells of the adjacent string (s) 410 are inverted emitter. Then, the emitter is located, already on the front face, and on the back face of the subcells. All subcells can have their emitter on the same side, but are formed on substrates of opposite doping types. The important thing is to have two families of subcells that have front faces F of different polarities.

This second variant of the manufacturing process according to the invention has the added advantage of being able to work with both bifacial cells and monofacial cells. On the contrary, unlike the previous proposals, it requires managing two different productions of photovoltaic cells. Since these cells do not necessarily have the same efficiency, the electrical current generated by the electrical module may be less than in the case of subcells of the same type (and of the same orientation).

The two variants of the manufacturing process described above can be put into practice whatever the nature of the interconnections, in the form of a strip or an electrical wire.

Figure 7 illustrates a second mode of implementation of the method according to the invention that does not involve cutting into half cells. Indeed, the full-size photovoltaic cells are cut, in the present case, only in the first direction 41, that is, perpendicular to the collecting fingers 12, thus obtaining sub-cells 70 in the form of a strip, for example three strips of 52 mm x 156 mm.

In step F2, groups 700 of sub-cells 70 are formed in the same way as previously described, with the difference that the groups 700 have dimensions similar to those of whole cells (for example, 158 mm x 156 mm). Thus, instead of a half-cell stringer, a whole cell stringer will be used with the same modification in correspondence with the aspiration nozzles and with the vision software. This is particularly advantageous as whole cell stringers are clearly more widespread and less expensive than half cell stringers and have a better rate of production. On the other hand, the gains in voltage will be more limited, as will the reduction of the resistive losses in the interconnections.

The other stages of the manufacturing process, in particular step F3 for interconnecting the subcells 70 in chains 710, can be carried out as previously indicated. Only the length of the interconnections 425 is adapted to the greater width of the subcells 70.

Thanks to the manufacturing process just described, a high voltage and low current photovoltaic module can be obtained easily and at a lower cost. At equivalent cell surface area, the module's open circuit voltage is multiplied by a factor equal to the number of sub-cells cut from a full-size cell. For its part, the electric current of the module is decreased in the same proportions.

For example, by cutting the 60 full-size photovoltaic cells of a conventional module by 6 (that is, 3 subcells per half cell), the module according to the invention can achieve an open circuit voltage greater than 220 V, in the case of solar cells. homojunction, and greater than 250 V in the case of heterojunction cells. Starting from 8 subcells per full-size photovoltaic cell (that is, 4 subcells per half cell), the open circuit voltage is greater than 300 V, in the case of homojunction cells, and greater than 340 V in the case of cells of heterojunction.

The elementary cells, or subcells, of the photovoltaic module according to the invention advantageously have a width l (in direction 41) less than or equal to the standard dimension of the photovoltaic cells (e.g. 156 mm) and a length L ^sc ( in direction 42) strictly less than its width. This is because the sub-cells have been made by cutting full-size photovoltaic cells perpendicular to the collector fingers. The photovoltaic module then includes fewer spacings between the sub-cells of the same string than in a module in which the sub-cells would have been trimmed parallel to the collector fingers. This increases the electrical power of the module per unit area. The fact that the module according to the invention includes, on the contrary, more chains and, therefore, more spacing between these chains, is not inconvenient, since these spacings are smaller than those between the sub-cells of a chain (approximately 1 mm, compared to 2.5mm between subcells).

In the preferred embodiment of Figures 4A to 4E, the width l of the subcells 40 is equal to the width of a half cell, that is, 78 mm, and the length L ^sc of the subcells 40 varies according to the number of subcells clipped from each cell 10. The length L ^sc of the sub-cells is preferably between 30.6 mm and 52.5 mm, which corresponds to 3-5 sub-cells per group 400, taking into account that certain cells of the group may have a longer length than others. Indeed, the upper end “52.5 mm” is the maximum length of the subcells with 1/6 format in the case of pseudo-square cells (52 mm for square cells) and the lower end “30.6 mm” is the length minimum of sub-cells with 1/10 format in the case of pseudo-square cells (31.2 for square cells).

Obtaining a high voltage, low current photovoltaic module has many advantages. A lower electrical current equates to lower resistive losses in the module interconnections, compared to conventional modules and therefore a better fill factor FF. Likewise, the resistive losses in the conductors of the photovoltaic installation are reduced, for example between two consecutive modules of a chain of modules. On the other hand, the fact of having a higher voltage at the output of the module makes it possible to equip each photovoltaic module with a microconductor, since the latter no longer needs to raise the voltage of the module to the level of the grid voltage. Before, this solution was not conceivable with conventional modules, due to the considerable cost of the microconductors. Since the step-up step of the microconductors is eliminated, their cost is reduced and one inverter per module, instead of a single inverter, can be provided for a whole chain of modules. A photovoltaic module that has its own inverter is of particular interest, as it is thus less sensitive to the disturbances that the module may experience, for example partial shading.

Of course, each photovoltaic cell or half cell can be cut into a greater number of subcells, for example 6, in order to further reduce the electrical current of the module and, with it, the resistive losses. However, the higher this number, the higher the rate of recombination of the charge carriers in the group of sub-cells, with respect to a cell or half-cell of equivalent size. And it is that a group of sub-cells includes numerous edges where the recombinations of charge carriers are concentrated. The best compromise between the decrease in the electrical current of the module and the recombination losses of the charge carriers is reached for subcells that have a width-to-length ratio between 1.48 and 2.55. A width to length ratio of 1.48 corresponds to the cut-off of three sub-cells 40 per half-cell 30 (Fig. 4A) or of three sub-cells 70 per full-size photovoltaic cell 10 (Fig. 7). A width to length ratio of 2.55 corresponds to the cutoff of five subcells 40 per half cell 30 or five subcells 70 per full-size photovoltaic cell 10.

The manufacturing process according to the invention also makes it possible to obtain photovoltaic modules whose efficiency and reliability are increased with respect to the photovoltaic modules with whole cells or with half cells of the prior art. These improvements are obtained by resizing the interconnections 420A-420C used in the stringing stage F3 (Figs. 4C, 5C and 7). Indeed, since the electric current is lower, the cross-section of the interconnections can be reduced without very significantly lowering the gains in terms of resistive losses (obtained by reducing the electric current).

The conductive wires used in step F3 within the scope of "SmartWire" and "Multi-Busbar" technology advantageously have a diameter less than or equal to 200 pm, and preferably less than or equal to 180 pm. When conductive strips are used, they advantageously have a width of less than or equal to 1 mm, for example 0.8 mm, and a thickness of less than or equal to 180 pm. In prior art photovoltaic modules, they typically have a width of 1.5 mm (3-tie rod configuration) or a width of 1.2 mm (4 tie-rod configuration), and a thickness greater than or equal to 200 pm.

By way of example, in a conventional photovoltaic module comprising a string of whole photovoltaic cells (156 mm x 156 mm) connected two by two by three strips of dimensions 1.5 mm x 0.2 mm, the cross section (i.e. , in direction 42) total of the interconnections is equal to 0.9 mm ² (that is, 5.77.10 ^-3 mm ² / mm, distributing the section over the entire length of the cells). By way of comparison, in a photovoltaic module comprising three strings of 52 mm x 78 mm sub-cells (sixths of cells) connected two by two by a single strip of dimensions 0.8 mm x 0.15 mm, the total cross section of the interconnections is equal to 0.36 mm ² (that is, 2.31.10 ^-3 mm ² / mm, distributing the section over the combined length of the sub-cells). Thus, the cross section is reduced by about 60%.

In the case of wire interconnections, “SmartWire” technology is usually implemented on whole photovoltaic cells (156 mm x 156 mm) with 18 wires of 300 pm in diameter, in order to obtain the best efficiency. The total cross section of these interconnections is then equal to 1.27 mm ² (that is, 8.14.10 ^-3 mm ² / mm). Thanks to the method according to the invention, (two to two) sixths of cells (52 mm x 78 mm) can be connected by six wires of 150 µm in diameter or four wires of 180 µm in diameter. The total cross section of conductor is then 0.31 mm ² approximately (ie 2,0.10 ^-3 mm ² / mm), which represents a reduction of approximately 75%.

For the realization of photovoltaic modules based on bifacial cells, which supply more current due to the contribution of the rear face, a slightly higher interconnection section can be used. For example, (two to two) sixths of cells (52mm x 78mm) can be connected by four 200 µm diameter wires, instead of 180 µm. The total conductor cross section is then about 0.37 mm ² (ie 2.4.10 ^-3 mm ² / mm).

Cross-sectional reductions can also be obtained with whole cells trimmed by 4, 8, or 10 subcells, instead of 6, with sharper reductions by increasing the number of subcells. Thus, when there are 3 to 5 subcells per group, the electrical wires advantageously have in each subcell a cross section translated to the length L ^sc of the subcell of less than 0.0025 mm ² / mm, and preferably less than 0. 0.0021 mm ² / mm.

The reduction of the cross-section of the interconnections leads to a decrease in the thermal expansion stresses in the interconnections and, consequently, to a better reliability of the photovoltaic modules. The interconnections, They are also more flexible, which allows the different groups of sub-cells to be brought closer together in order to make more compact modules. For example, the space between two consecutive sub-cell groups can be less than 1.3 mm using 150 gm diameter wires or less. In other words, the sub-cells of each chain are equally spaced in direction 41 at a distance less than or equal to 1.3 mm, for example 1 mm. In direction 42, the sub-cell chains are advantageously spaced two by two at a distance less than or equal to 1.0 mm.

Reducing the cross-section of the interconnections further allows, in the case of conductive wires, to reduce the cost of manufacturing the module. In effect, this reduces the quantity of the alloy that covers the copper cores of the wires and that allows them to be brazed on the connecting bars or the collector fingers. This is particularly true for “SmartWire” technology, where the coating of the conductive wires is based on indium, a material that is very expensive. For example, going from 300 gm diameter wires to 150 gm diameter wires, the amount of indium is divided by two (the thickness of the alloy layer is constant, only its perimeter decreases).

Reducing the cross-section of the interconnections also leads to an increase in the electrical power of the photovoltaic modules, since the shading caused by the interconnections is less. In this way, the subcells produce more current for the same insolation. These current gains are even more significant with conductive wires, because, due to their cylindrical shape, the effective shading does not correspond to more than 70% of the diameter of the wires. For example, for a 150 gm diameter wire, the actual shading is no more than 105 gm wide.

In this way, when the manufacturing process of the invention is combined with the "SmartWire" interconnection technology, highly reliable photovoltaic modules can be obtained at low cost (lower amounts of silver and indium) (absence of voltages in handling of chains, few thermal expansion stresses) and high efficiency (resistive losses, shading).

Obviously, the manufacturing method according to the invention is not limited to the embodiments described with reference to Figures 4 to 7, and other variants will become apparent to a person skilled in the art. In particular, the manufacturing process is applicable in all types of photovoltaic cells, homojunction or heterojunction, based on silicon (monocrystalline, multicrystalline, amorphous).

Claims (17)

1. Manufacturing process of a photovoltaic module that successively comprises the following stages: - providing photovoltaic cells (10) including collector fingers (12); - cutting (F1) the photovoltaic cells (10) according to a first direction (41) perpendicular to the collector fingers to form a plurality of sub-cells (40, 70); - aligning (F2) subcells (40, 70) in a second direction (42) perpendicular to the first direction (41), in order to constitute groups (400, 700) of electrically isolated subcells, each group of subcells having one dimension ( L ') in the second direction (42) substantially identical to the dimension (L) of the photovoltaic cells (10) in the second direction; - forming (F3) simultaneously a plurality of chains (410, 710) of subcells connected in series, successively aligning the groups (400, 700) of subcells (40, 70) in the first direction (41) and interconnecting the groups (400 , 700) of aligned sub-cells (40, 70), the sub-cells (40, 70) of each group (400, 700) being simultaneously grasped and belonging to chains (410, 710) of different sub-cells; and - connect (F4-F5) electrically in series the chains (410, 710) of subcells (40, 70). Method according to claim 1, in which the subcells (40) are obtained by cutting the photovoltaic cells (10) once according to the second direction (42) and at least once according to the first direction (41). Method according to claim 2, in which the photovoltaic cells (10) are cut according to the second direction (42) into two half cells (30) of the same surface area and in which the half cells (30) are cut according to the first direction (41) to form the subcells (40). Method according to any one of claims 1 to 3, in which the groups (400, 700) of subcells (40, 70) are interconnected two by two by means of electrical wires (420A) so that each face ( F, B) of the subcells is in contact with a plurality of electrical wires (420A). 5. Method according to claim 4, in which the electrical wires (420A) are integral with a support made of polymer material and are in contact with the collector fingers (12) of the sub-cells (40). Method according to claim 5, in which the groups (400) of subcells (40) are interconnected by pressing a support sheet (430A) on both sides of each group of subcells, the electrical wires (420A) being distributed in the surface of each support sheet in contact with the group of subcells, and in which the support sheets (430A) are subsequently trimmed to separate the different chains (410) of subcells (40). 7. Method according to claim 5, in which the groups (400) of sub-cells (40) are interconnected by pressing several differentiated pieces (430 ') of the support on both sides of each group of sub-cells, electrical wires (420A) being distributed on the surface of each piece of the support in contact with the group of subcells, and in which each piece (430 ') of the support belongs to a single chain (410) of subcells (40). 8. Process according to any one of claims 4 to 7, in which the electric wires (420A) have a diameter less than or equal to 200 gm. Method according to any one of Claims 1 to 8, in which the sub-cells (40, 70) belonging to the chains (410, 710) of sub-cells connected in series are of the same type and are oriented in the same direction. Method according to any one of claims 1 to 8, in which the sub-cells (40, 70) belonging to a first chain (410, 710) and the sub-cells belonging to a second chain (410, 710) adjacent to the first chain are of opposite types or are oriented in opposite directions. 11. System that makes it possible to interconnect portions (40, 70) of photovoltaic cell, the portions of photovoltaic cell comprising collector fingers (12) oriented perpendicular to a first direction (41), characterized by including: - a charging station configured to distribute groups (400, 700) of several cell portions electrically isolated and aligned in a second direction (42) perpendicular to the first direction (41), each group (400, 700) having portions of cell with a dimension (L ') in the second direction (42) substantially identical to the dimension (L) of the photovoltaic cell in the second direction (42); - an assembly station configured to interconnect in the first direction (41) the groups (400, 700) of cell portions (40, 70) in order to simultaneously form a plurality of chains (410, 710) of cell portions, the cell portions of each group belonging to chains of portions of different cell; - a first transfer unit configured to capture each group (400, 700) of cell portions and move said group of cell portions from the loading station towards the assembly station, the cell portions (40, 70 being simultaneously grasped ) of each group (400, 700). System according to claim 11, wherein the first transfer unit comprises aspiration nozzles configured to simultaneously aspirate all cell portions (40, 70) of said group (400, 700). System according to one of claims 11 and 12, comprising a station for cutting photovoltaic cells (10) into cell portions (40, 70), located upstream of the charging station. System according to any one of claims 11 to 13, comprising a module for distributing electrical wires (420A) integral with a support (430A), and in which the assembly station is configured to mechanically link the support of the electrical wires with the groups (400, 700) of cell portions (40, 70). System according to claim 14, comprising a cutting device configured to trim the support (430A) of the electric wires (420A) after the assembly of the groups (400, 700) of cell portions (40, 70), in order to separate the chains (410, 710) of cell portions. System according to any one of claims 11 to 15, comprising a second transfer unit configured to individually grasp each of the chains (410, 710) of cell portions (40, 70) coming from the assembly station and to rotate the grasped chain 180 °. System according to any one of claims 11 to 15, comprising a second transfer unit configured to collectively grasp several chains (410, 710) of cell portions (40, 70) from the assembly station, to release a first part of said grasped chains and to rotate 180 ° a second remaining part of said grasped chains.